Heteronudear correlations

Proton-Detected, Long-Range H—13C Heteronudear Correlation HMBC 265... 

Uniform and labeling provides improved signal dispersion and editing by multidimensional experiments or filtering by isotope or spin-state as well as various routes for coherence transfer and ways to measure scalar and dipolar couplings. Solvent suppression in heteronudear correlation experiments is also much easier than in homonuclear correlation experiments. 

Many multipulse NMR experiments are based on coherence selection, where it is desirable to detect only one of two or more signal components, and the remaining signal components must be eliminated from the spectrum. Examples of this are H C heteronudear correlation experiments such as HSQC, HMQC, HMBC, and H2BC (Table 4), where it is desirable to detect 1% of the proton signal from coupled to... 

Kessler, H., Griesinger, C., Zarbock, J., Loosli, H. R. Assignment of carbonyl carbons and sequence analysis in peptides by heteronudear shift correlation via small coupling constants with broad-band decoupling in ft (COLOC)./. Magn. Reson. 1984, 57, 331-336. 

Heteronudear shift correlation spectroscopy is a 2D technique that can be used to determine the connectivity of H and C nuclei (or other heteronuclei), formally bonded together through one or more chemical bonds. The corresponding experiments make use of either the large or the smaller long-range "Jv, couplings for polarization transfer. 

In 2003, Appleton and Copp [102] reported the isolation and characterization of another related alkaloid, kottamide-E (84) again making use of long-range H- N heteronudear chemical shift correlation data. 

HSQC. The Heteronudear Single Quantum Correlation (HSQC) experiment is an alternative to HMQC that accomplishes a similar objective. The experiment generates, via an INEPT sequence, single quantum (or " N) coherence, which evolves and then is transferred back to the proton frequency by a second INEPT sequence, this time in reverse. The main difference from the HMQC result is that HSQC spectra do not contain H- H couplings in the C ( Jj) dimension. As a result, HSQC cross peaks tend to have improved resolution over analogous HMQC cross peaks. HSQC is preferred when there is considerable spectral overlap. 

The conclusions reached here apply equally well to general multi-electron homonuclear molecules. In this case the value of in the dissociation limit becomes equal to the sum of the contributions of the atomic fragments. The A-integrated exchange-correlation hole for a reference electron on one of the atomic fragments will then be equal to the A-integrated hole of the atom itself. The properties of the exchange-correlation in heteronudear molecules are discussed in the next section. 

For studies of protein complexes intermolecular correlations can be distinguished from intramolecular correlations by filtered heteronudear experiments, provided that one of the components is labeled selectively and differentiy from the other. This approach is also useful for large protein complexes to acquire simplified spectra to alleviate the assignment For the same end, segments of a poly-... 

Martin, G.E. and Hadden, C.E. (2000) Long-range heteronudear shift correlation at natural abundance. J. Nat. Prod., 63, 543-585. 

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